It has been long recognized that the cutting performance of a knife can be enhanced or made to suit a particular cutting purpose by providing at the cutting edge a formulation such as serrations or scallops. However, whilst such formulations can improve considerably the cutting action, they have the disadvantage of not readily being resharpenable and have a tendency to tear rather than cut clean. Because the creation of formulations such as serrations or scallops involves a separate grinding step in the production of knife blades, this has the effect of increasing production costs, and yet produces a blade which may not have the total life of a conventional blade by virtue of the difficulties of resharpening. It is, therefore, most important that the production costs of a blade with edge formulations are kept to a minimum, whilst providing adequate cutting life and improved cutting performance.
The long recognition of the effect of serrating a cutting edge is shown by U.S. Pat. No. 1,911,974 where one side of a blade blank is flat ground, and the opposite side ground at an angle with serrations to produce the known chisel edge construction, where the cutting tip of the blade is co-planar with one side face of the blade. At its date, and when hand grinding was the common practice, the blade would be repeatedly presented to a relatively narrow grinding wheel to produce groups of serrations at the same time. Therefore, to assist the operative to present the knife blanks to the wheel, the blade would have been initially notched at spaced intervals along its length, the spacing of the notches being equivalent to the width of the wheel. By this, the operative had a visual reference point to assist in ensuring that on presenting the blank a second or subsequent time to a wheel, there would be no overgrinding of second serrations on serrations already formed, with the effect that would have on creating a jagged edge of impaired performance, and on visual appearance of the serrated edge. It will, therefore, be understood that the spaced notches displayed in U.S. Pat. No. 1,911,974 were not intended to, and do not take part in the cutting action of the knife, and by its nature and having a chisel edge, has the disadvantage that when cutting, the applied forces to the chisel edge made cutting in a straight vertical direction difficult, these applied forces tending to cause the blade to move in an angular direction through the substance being cut.
In U.S. Pat. No. 2,059,414, the problems associated with the chisel edge of U.S. Pat. No. 1,911,974 are avoided by generating a centre vee at one edge of a blank, by grinding both sides of the blank with serrations, at the additional cost of grinding both sides of the blank edge at the required angle. Being specifically designed for cutting bread, the proposal of U.S. Pat. No. 2,059,414 is to provide an effective saw-like structure by slotting the blank at spaced intervals along its length to provide a number of distinct teeth, and where each tooth has a sharpened forward and trailing edge, and an outer edge sharpened by the grinding of serrations to both sides as mentioned above. Whilst such a saw-tooth-like construction might function in the manner indicated to reduce or eliminate the creation of crumbs whilst cutting bread, it is a form of construction unsuited to the cutting of other substances, particularly food substances such as meat, vegetables and fruit.
A formation of cutting edge that combines the advantages of a centre cutting Y-edge edge to a knife blade, and hence the avoidance of the known disadvantages of a chisel-edge, with the provision of cutting formulations such as serrations and/or scallops, and with attendant reduced manufacturing costs is disclosed in British Pat. No. 2,108,887. Here, a continuous cutting edge is formed by providing the blade with a V-shaped cutting edge, centrally located on a parallel-sided blank, the cutting edge being flat ground to one side of the Vee and ground with formulations to the opposite side of the Vee. Such a construction has proved to be most effective in providing an exceedingly sharp cutting edge that retains its sharpness for considerable periods, and can be resharpened, by avoiding the provision of serrations to both sides of the centre cutting vee, at the additional cost involved. The further advantage of this cutting edge is its wide applicability to food substances at large.
However, extensive usage of the edge construction of British Pat. No. 2,108,887 has shown that it is capable of still further improvement, and it is the object of the present invention to provide such further improvements.